1. Field of the Invention
The invention relates to a cutting device for cutting limply flexible material, such as e.g. fabric layers, leather skins or the like.
2. Description of the Related Art
A cutting device of the kind concerned includes a cutting table, the table surface of which carries a cutting support on which the material can be spread out. Further, a cutting head is provided, which cutting head is so arranged above the table surface that it is movable above the surface. A cutting tool, provided at the cutting head, is brought into engagement with the material to be cut by lowering down, in order to cut the material in correspondence to a given pattern. Thereby, the cutting tool completely penetrates through the material to be cut and penetrates into the cutting support.
In conventional devices of this kind there is used as cutting support a material which is suitable, through the pressure of the cutting tool, frequently a cutting wheel, on the cutting support, to cut through the material to be cut lying thereupon. Thereby, the cutting tool can penetrate more or less into the cutting support, for example also to cut the cutting support and/or to elastically deform it. The cutting support usually lies on a table, whereby very frequently the cutting support and the material to be cut lying thereupon are held against the table by vacuum suction. Significant with such devices is that, on the one hand, the cutting tool always penetrates through the material to be cut but does not penetrate through the cutting support itself as far as the means on which it is carried, since with too strong a penetration into the cutting support the cutting tool could break or be destroyed on the table. Conventionally, the pressure exercised by the cutting tool on the material to be cut or on the cutting support is detected and from this the cutting head carrying the cutting tool is adjusted in its height. It is however necessary, in dependence upon the material to be cut in each case and the thickness of the material to be cut in each case, to specially set the pressure which, for the follow-up device employed, is to be regarded as desired pressure. Further, it has also to be taken into account that different tools, because of their different configurations, also give rise to different cutting resistances, for which reason the corresponding desired pressure must in each case be newly set in dependence thereupon. The pressure setting is, however, rather time consuming and complex. With materials the stiffness of which and the thickness of which vary, for example leather, an appropriate setting of the desired pressure is only possible to a limited extent. Thus, with the devices according to the state of the art, it cannot be ensured that the material to be cut is always reliably separated, the cutting tool, however, not penetrating too deeply into the cutting support.
The penetration depth of the cutting heads of known cutting devices can be so set in dependence upon the material to be cut, e.g. by means of a variable weight loading or a variable spring biasing, that the cutting tool penetrates into the material carrier with a certain penetration depth.
With a penetration depth which is too small there is the danger that the material to be cut will not be completely separated or will not be cleanly cut.
When, on the other hand, the cutting tool penetrates too deeply into the cutting support, there is the disadvantage of premature wear of the cutting support as a result of the deep cutting grooves which are formed. Further, in the case of a too deep entry of the cutting tool into the cutting support, there is the danger of blade breakage which in practice frequently occurs in particular when cutting tight radiuses. The time then required for changing the cutting tool significantly increases production costs.
A further disadvantage consists in that with constantly changing different materials to be cut, the structures and material thicknesses of which and thus the cutting resistances of which vary significantly, the application pressure of the cutting tool must be newly set with each change of material, in order to achieve a constant penetration depth. In practice this is not possible without unacceptable expenditure of effort. A further problem which also applies is that the cutting pressure and thus the penetration depth into the cutting support additionally change in dependence upon the sharpness of the cutter.
With the employment of a cutting head having a plurality of cutting tools there is further the problem that the different cutting tools, because of their different configurations, experience different resistances upon penetration of the material to be cut, which makes necessary a different setting of the application pressure for the different tools.